Prostaglandin D2 (hereinafter referred to as “PGD2”) are known as a metabolite in the arachidonic acid cascade, and are thought to be one of chemical transmitters that take part in allergic disease, for example, allergic rhinitis, bronchial asthma, and conjunctivitis allergic. It has been known that PGD2 is produced from mast cells and free PGD2 shows bronchoconstriction, permeability accentuation, vasodilation or shrinkage, mucus secretion promotion, and platelet aggregation inhibitory effect. It has been reported that PGD2 induces airway contraction and rhinostenosis symptom in vivo and the increase in PGD2 concentration has been recognized in the pathologic topical of systemic mast cytosis (mastocytosis) patients, nasal allergy patients, bronchial asthma patients, atopic dermatitis patients, and urticaria patients, etc (New Eng. J. Med., 303, 1400–1404 (1980), Am. Rev. Respir. Dis., 128, 597–602 (1983), J. Allergy Clin. Immunol., 88, 33–42 (1991), Arch Otolaryngol Head Neck Surg, 113, 179–83 (1987), J. Allergy Clin. Immunol., 82, 869–77 (1988), J. Immunol., 146, 671–6 (1991), J. Allergy Clin. Immunol., 83, 905–12 (1989), N. Engl. J. Med., 315, 800–4 (1986), Am. Rev. Respir. Dis., 142, 126–32 (1990), J. Allergy Clin. Immunol., 87, 540–8 (1991), J. Allergy Clin. Immunol., 78, 458–61 (1986)). Also, PGD is considered to relate to neuro activities, especially, sleep, hormone secretion, and pain. Furthermore, there are reports suggesting participations in platelet aggregation, glycogen metabolism, ocular tension adjustment and the like.
PGD2 shows its effects by binding to DP receptor which is one of receptor thereof. A DP receptor antagonist binds and is antagonistic to its receptor so that it can inhibit the function. Accordingly, it is considered to be useful for the prevention and/or treatment of diseases, for example, allergic diseases (allergic rhinitis, allergic conjunctivitis, atopic dermatitis, bronchial asthma, food allergy, etc.), systemic mastocytosis, disorders due to systemic mastocyte activation, anaphylactic shock, bronchoconstriction, urticaria, eczema, allergic bronchopulmonary aspergillosis, paranasal sinusitis, migraine, nasal polyp, hypersensitive angitis, eosinophilia, contact dermatitis, diseases accompanied with itching (such as atopic dermatitis, urticaria, allergic conjunctivitis, allergic rhinitis, contact dermatitis, etc.), secondary diseases (such as cataracta, retinodialysis, inflammation, infection, dysgryphia, etc.) generated by behaviors caused by itching (scratching behaviors, beating, etc.), inflammation, chronic obstructive pulmonary disease, ischemic reperfusion disorder, cerebrovascular disorder, pleuritis complicated by rheumatoid arthritis, ulcerative colitis and the like. Moreover, it is considered to relate to sleeping and platelet aggregation and to be useful for these diseases.
It is known that PGD2 binds with chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2 besides DP receptor, and has the migration action on Th 2 cell, eosinophil, and basophil (J. Exp. Med., 193, 255–261 (2001), Blood, 98, 1942–1948 (2001)). Since PGD2 is a ligand to both of DP and CRTH2 receptors in vivo, DP receptor antagonists are expected to bind with CRTH2 receptor, and to antagonize the biological activity.
So, it is considered to be useful for the prevention and/or treatment of diseases, allergic diseases, for example, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, bronchial asthma, food allergy, etc., systemic mastocytosis, disorders due to systemic mastocyte activation, anaphylactic shock, bronchoconstriction, urticaria, eczema, allergic bronchopulmonary aspergillosis, paranasal sinusitis, migraine, nasal polyp, hypersensitive angitis, eosinophilia, contact dermatitis, diseases accompanied with itching such as atopic dermatitis, urticaria, allergic conjunctivitis, allergic rhinitis, contact dermatitis, etc.; secondary diseases such as cataracta, retinodialysis, inflammation, infection, dysgryphia, etc. generated by behaviors caused by itching (scratching behaviors, beating, etc.), inflammation, chronic obstructive pulmonary disease, ischemic reperfusion disorder, cerebrovascular disorder, pleuritis complicated by rheumatoid arthritis, ulcerative colitis and the like.
Some PGD2 receptor antagonists are known conventionally, and BW-A868C represented by the following formula (A) is considered to be the most selective:

Recently, PGD2 receptor antagonists comprising thromboxane derivatives have been published in WO 98/25915, WO 98/25919, WO 97/00853, WO 98/15502 and the like.
As prostaglandin receptors, a lot of receptor including the subtype exist and the pharmacological action is respectively different. Then, if new compounds that weakly bind to other prostaglandin receptors and specifically bind to PGD2 receptor, especially DP receptor can be found, there is a possibility to become a medicine having a little side effect because of disappear of other actions, and discovery of such a medicine is necessary.